3D-HEVC inter-frame information hiding method based on visual perception

ABSTRACT

A 3D-HEVC inter-frame information hiding method based on visual perception includes steps of information embedding and information extraction. In the step of information embedding, the human visual perception characteristic is considered, stereo salient images are obtained by a stereo image salient model, and the stereo salient images are divided into salient blocks and non-salient blocks with an otsu threshold. The coding quantization parameters are modified according to different modulation rules for different regions. Then, based on the modified quantization parameters, the coding-tree-units are coded to complete the information embedding. In the step of information extraction, no original video is needed, no any side information needs to be transmitted, and the secret information can be blindly extracted. The present invention combines with the human visual perception characteristic, and selects P frames and B frames as embedded frames for effectively reducing the decrease of the stereo video subjective quality.

CROSS REFERENCE OF RELATED APPLICATION

The present invention claims priority under 35 U.S.C. 119(a-d) to CN201710202076.6, filed Mar. 30, 2017.

BACKGROUND OF THE PRESENT INVENTION Field of Invention

The present invention relates to a video information hiding technology,and more particularly to a 3D-HEVC inter-frame information hiding methodbased on visual perception.

Description of Related Arts

The three dimensional (3D) video can give users a new visual impact andhas aroused widespread concern. With the maturity of the internettechnology, the 3D video can be easily handled illegally, so that thesecurity of the 3D video has become a major problem restricting thecommercialization of 3D products. The information hiding technology caneffectively accomplish the secret communication and copyright judgmentof multimedia data, so it can better solve the information securityproblem in the video coding transmission. The 3D video has a largeamount of data, so it needs to be efficiently compressed so as to savethe transmission bandwidth and storage space. JCT-3V, composed of ITU-TVideo Coding Experts Group and ISO/IEC Motion Picture Experts Group, isdedicated to the study of 3D-HEVC (3D High Efficiency Video Coding)coding standard. Therefore, the study on the 3D video information hidingtechnology based on 3D-HEVC standard is a subject with both academic andapplication value.

At present, the study on the 3D video information hiding technologystill has a big problem. In accordance with the embedded location, the3D video information hiding technology can be divided into the hiddenalgorithm of the original domain and the hidden algorithm of thecompressed domain. The hidden algorithm of the original domain isdefined as embedding the secret information in the original video whichis not coded and compressed. For example, YANG et al. proposed a 3Dvideo blind watermarking algorithm based on quantized index modulation,which embeds the watermarking information into the DCT coefficients ofthe depth video. This algorithm has a strong robustness and the colorvideo is not distorted. The 3D video needs to be coded and transmitted,the hidden algorithm of the original domain cannot be directly appliedto the compressed domain, otherwise it will cause the loss of the secretinformation. The existing 3D video information hiding technology of thecompressed domain is mainly based on the 3D video coding standardexpansion of H.264. For example, SONG et al. proposed a reversiblemulti-view video information hiding algorithm, which through introducingthe idea of the inner product, the information hiding is carried out onthe motion vector of the b4 frame coding block. This method has betterimperceptibility and can realize the information reversibility. Thecompression performance of the 3D-HEVC coding standard is significantlybetter than that of the 3D video coding standard expansion based onH.264, and is adapted for the coding of the more high-definition videosequence, so the study on the 3D video information hiding algorithmbased on the 3D-HEVC coding standard is necessary. At present, theembedded vectors selected by video information hiding technology aremainly intra prediction modes, DCT coefficients, motion vectors and soon. These common embedded vectors are vulnerable to illegal attacks,which undoubtedly reduces the security of the video information hidingtechnology. At the same time, due to different attentions of the humaneye on different areas of a same video, the more concerned region cantolerate less distortion, the less concerned region can tolerate greaterdistortion, and the existing inter-frame information hiding algorithmjust simply uses the secret information to modulate the video codingparameters, does not consider the perception characteristic of the humanvisual system (HVS), and is unable to improve the algorithm performanceto the maximum. Therefore, it needs to research a 3D-HEVC inter-frameinformation hiding method based on visual perception.

SUMMARY OF THE PRESENT INVENTION

A technical problem to be solved of the present invention is to providea 3D-HEVC inter-frame information hiding method based on visualperception, which combines with human visual perception characteristicand uses P frames and B frames as embedded frames for effectivelyreducing the decrease of the stereoscopic video subjective quality, islow in computational complexity, has small impact on bit rate, and canachieve blind extraction.

A technical solution adopted by the present invention to solve the abovetechnical problem is as follows. A 3D-HEVC inter-frame informationhiding method based on visual perception comprises steps of informationembedding and information extraction, wherein:

the step of information embedding comprises:

(1A) at an information embedding terminal, taking S_(org) as an originalstereo video, recording a left view color video of the S_(org) asL_(org), recording a right view color video of the S_(org) as R_(org),and taking W as secret information to be embedded, wherein: W is abinary number which contains n_(w) bits, W=w_(n) _(W) w_(n) _(W) ₋₁ . .. w_(i) . . . w₂w₁, a width of both a left view color image of theL_(org) and a right view color image of the R_(org) is M, a heightthereof is N, both the M and the N can be divisible by 64, a total framenumber of both all left view color images of the L_(org) and all rightview color images of the R_(org) is F, here, F≧1, n_(W) is a integer and

${n_{W} \in \left\lbrack {2,\frac{2 \times M \times N \times F}{64 \times 64}} \right\rbrack},$

w_(n) _(W) w_(n) _(W) ₋₁ . . . w_(i) . . . w₂w_(w) respectivelyrepresent a value of a (n_(W))^(th) bit, a value of a (n_(W)−1)^(th)bit, . . . , a value of an i^(th) bit, . . . , a value of a second bitand a value of a first bit, each of the w_(n) _(W) w_(n) _(W) ₋₁ . . .w_(i) . . . w₂w₁ is 0 or 1, 1≦i≦n_(W);

(1B) obtaining a stereo saliency image of each left view color image ofthe L_(org) through a stereo image saliency model, recording a stereosaliency image of a j^(th) left view color image of the L_(org) asL_(org,j) ^(u), calculating an otsu threshold of the stereo saliencyimage of each left view color image of the L_(org), and recording theotsu threshold of the P_(org,j) ^(u) as y_(j) ^(L), wherein 1≦j≦F,

also, obtaining a stereo saliency image of each right view color imageof the R_(org) through the stereo image saliency model, recording astereo saliency image of a j^(th) right view color image of the R_(org)as R_(org,j) ^(u), calculating an otsu threshold of the stereo saliencyimage of each right view color image of the R_(org), and recording theotsu threshold of the R_(org,j) ^(u) as y_(j) ^(R);

(1C) dividing the stereo saliency image of each left view color image ofthe L_(org) into non-overlapped

$\left( {\frac{M}{64} \times \frac{N}{64}} \right)$

image blocks each of which has a size of 64×64, recording a k^(th) imageblock of the L_(org,j) ^(u) as B_(org,j,k) ^(L), calculating a meanvalue of pixel values of all pixels of each image block of the stereosaliency image of each left view color image of the L_(org) recordingthe mean value of the pixel values of all the pixels of the B_(org,j,k)^(L) as q_(j,k) ^(L), determining whether each image block of the stereosaliency image of each left view color image of the L_(org) is a salientblock or a non-salient block according to the mean value of the pixelvalues of all the pixels of each image block of the stereo saliencyimage of each left view color image of the L_(org) and the otsuthreshold of the stereo saliency image of each left view color image ofthe L_(org), wherein: if the q_(j,k) ^(L) is larger than or equal to they_(j) ^(L), the B_(org,j,k) ^(L) is determined to be the salient block,if the q_(j,k) ^(L) is smaller than the y_(j) ^(L), the B_(org,j,k) ^(L)is determined to be the non-salient block, here,

${1 \leq k \leq {\frac{M}{64} \times \frac{N}{64}}},$

also, dividing the stereo saliency image of each right view color imageof the R_(org) into non-overlapped

$\left( {\frac{M}{64} \times \frac{N}{64}} \right)$

image blocks each of which has a size of 64×64, recording a k^(th) imageblock of the R_(org,j) ^(u) as B_(org,j,k) ^(R), calculating a meanvalue of pixel values of all pixels of each image block of the stereosaliency image of each right view color image of the R_(org), recordingthe mean value of the pixel values of all the pixels of the B_(org,j,k)^(R) as q_(j,k) ^(R), determining whether each image block of the stereosaliency image of each right view color image of the R_(org) is asalient block or a non-salient block according to the mean value of thepixel values of all the pixels of each image block of the stereosaliency image of each right view color image of the R_(org) and theotsu threshold of the stereo saliency image of each right view colorimage of the R_(org), wherein: if the q_(j,k) ^(R) is larger than orequal to the y_(j) ^(R), the B_(org,j,k) ^(R) is determined to be thesalient block, if the q_(j,k) ^(R) is smaller than the y_(j) ^(R), theB_(org,j,k) ^(R) is determined to be the non-salient block;

(1D) generating a binary pseudorandom sequence which contains n_(W) bitsthrough logistics chaotic mapping, taking the binary pseudorandomsequence as a secret key and recording the secret key as E, here,E=e_(n) _(W) e_(n) _(W) ₋₁ . . . e_(i) . . . e₂e₁, perform an XOR(exclusive OR) operation on a value of each bit of the W and a value ofeach corresponding bit of the E, obtaining an XOR result, taking the XORresult as encrypted information and recording the encrypted informationas W′, here, W′=w′_(n) _(W) w′_(n) _(W) ₋₁ . . . w′_(i) . . . w′₂ w′₁,wherein: the e_(n) _(W) e_(n) _(W) ₋₁ . . . e_(i) . . . e₂e₁respectively represent a value of the (n_(W))^(th) bit, a value of the(n_(W)−1)^(th) bit, . . . , a value of the (i)^(th) bit, . . . a valueof the second bit and a value of the first bit of the E, each of thee_(n) _(W) e_(n) _(W) ₋₁ . . . e_(i) . . . e₂e₁ is 0 or 1, w′_(n) _(W)w′_(n) _(W) ₋₁ . . . w′_(i) . . . w′₂ w′₁ respectively represent a valueof the (n_(W))^(th) bit, a value of the (n_(W)−1)^(th) bit, . . . , avalue of the (i)^(th) a value of the second bit and a value of the firstbit of the W′, each of the w′_(n) _(W) w′_(n) _(W) ₋₁ . . . w′_(i) . . .w′₂ w′₁ is 0 or 1, w′_(i) is an XOR value of the w_(i) and the e_(i);

(1E) coding the L_(org) and the R_(org) in frame through a 3D-HEVCstandard coding platform, defining a j^(th) left view color image of theL_(org) to be coded or a j^(th) right view color image of the R_(org) tobe coded as a current frame and recording the current frame as P_(j),wherein an initial value of the j is 1;

(1F) judging whether the P_(j) is a P-frame or a B-frame, wherein if itis, step (1G) is executed, if it is not, step (1I) is executed;

(1G) coding the P_(j) in coding-tree-unit, defining a k^(th)coding-tree-unit to be coded of the P_(j) as a current coding block andrecording the current coding block as B_(org,j,k), wherein

${1 \leq k \leq {\frac{M}{64} \times \frac{N}{64}}},$

here an initial value of the k is 1;

(1H-a) reading coding quantization parameter of the B_(org,j,k) andrecording the coding quantization parameter as QP_(org,j,k), reading avalue w′_(i), of a i′^(th) bit of the W′ and a value w′_(i′+1) of a(′+1)^(th) bit of the W′, transforming the w′_(i′+1) and the w′_(i),into decimal value and recording the decimal values as d_(i′), here,

$\left\{ {\begin{matrix}0 & {{w_{i^{\prime} + 1}^{\prime}w_{i^{\prime}}^{\prime}} = 00} \\1 & {{w_{i^{\prime} + 1}^{\prime}w_{i^{\prime}}^{\prime}} = 01} \\2 & {{w_{i^{\prime} + 1}^{\prime}w_{i^{\prime}}^{\prime}} = 10} \\3 & {{w_{i^{\prime} + 1}^{\prime}w_{i^{\prime}}^{\prime}} = 11}\end{matrix},} \right.$

wherein an initial value of the i′ is 1≦i′≦n_(W)−1, and each of w′_(i′)and w′_(i′+1) is 0 or 1;

(1H-b) when the P_(j) is the j^(th) left view color image of theL_(org), judging whether a remainder result of the QP_(org,j,k) to 4 isequal to the d_(i′), wherein if the remainder result is not equal to thed_(i′), when the B_(org,j,k) ^(L) is a salient block, the QP_(org,j,k)is downwardly modulated by the w′_(i), and the w′_(i′+1), so that codingquantization parameter embedded with secret information of theB_(org,j,k) ^(L) is obtained and recorded as QP′_(org,j,k), and thenstep (1H-c) is executed; when the B_(org,j,k) ^(L), is a non-salientblock, the QP_(org,j,k) is upwardly modulated by the w′_(i), and thew′_(i′+1), so that the coding quantization parameter embedded withsecret information of the B_(org,j,k) is obtained and recorded as theQP′_(org,j,k), and then the step (1H-c) is executed; if the remainderresult is equal to the d_(i′), the QP_(org,j,k) is directly recorded asthe coding quantization parameter embedded with secret information ofthe B_(org,j,k) which is denoted as the QP′_(org,j,k),QP′org,j,k=QP_(org,j,k), and then the step (1H-c) is executed, here, “=”is an assignment symbol in the QP′_(org,j,k)=QP_(org,j,k);

when the P_(j) is the j^(th) right view color image of the R_(org),judging whether a remainder result of the QP_(org,j,k) to 4 is equal tothe d_(i′), wherein if the remainder result is not equal to the d_(i′),when the B_(org,j,k) ^(R) is a salient block, the QP_(org,j,k)downwardly modulated by the w′_(i′) and the w′_(i′+1), so that codingquantization parameter embedded with secret information of theB_(org,j,k) is obtained and recorded as QP′_(org,j,k), and then the step(1H-c) is executed; when the B_(org,j,k) ^(R) is a non-salient block,the QP_(org,j,k) upwardly modulated by the w′_(i′) and the w′_(i′+1), sothat the coding quantization parameter embedded with secret informationof the B_(org,j,k) is obtained and recorded as the QP′_(org,j,k), andthen the step (1H-c) is executed; if the remainder result is equal tothe d_(i′), the QP_(org,j,k) is directly recorded as the codingquantization parameter embedded with secret information of theB_(org,j,k) which is denoted as the QP′_(org,j,k),QP′_(org,j,k)=QP_(org,j,k), and then the step (1H-c) is executed;

(1H-c) judging whether the QP′_(org,j,k) is in a range of [0, 51],wherein if it is, step (1H-d) is executed; otherwise, whenQP′_(org,j,k)51, the QP_(org,j,k) is downwardly modulated by the w′_(i′)and the w′_(i′+1) the coding quantization parameter embedded with secretinformation QP′_(org,j,k) of the B_(org,j,k) is obtained again, and thenthe step (1H-d) is executed; when QP′_(org,j,k)<0, the QP_(org,j,k) ismodulated the w′_(i′), and the w′_(i′+1), the coding quantizationparameter embedded with secret information QP′_(org,j,k) of theB_(org,j,k) is obtained again, and then the step (1H-d) is executed;

(1H-d) coding the B_(org,j,k) with the QP′_(org,j,k), completing asecret information embedded process of the B_(org,j,k), after completingcoding of the B_(org,j,k), judging whether the B_(org,j,k) is a skipblock, wherein if it is, step (1H-e) is directly executed, otherwise,i′=i′+2 is set, the step (1H-e) is executed, here, “=” is an assignmentsymbol in the i′=i′+2;

(1H-e) setting k=k+1, regarding a next coding-tree-unit to be coded ofthe P_(j) as a current coding block and recording the nextcoding-tree-unit to be coded as B_(org,j,k), returning to the step(1H-a) to continue till all coding-tree-units of the P_(j) arecompletely coded, executing step (1I), wherein “=” is an assignmentsymbol in the k=k+1;

(11) setting j=j+1, regarding a next left view color image to be codedof the L_(org) or a next right view color image to be coded of theR_(org) as a current frame and recording the current frame as P_(j),returning to the step (1F) and continuing till all left view colorimages in the L_(org) and all right view color images in the R_(org) arecompletely coded, and obtaining video stream embedded with secretinformation, wherein “=” is an assignment symbol in the j=j+1; and

(1J) sending initial value information which generates the secret key Eto an information extraction terminal.

The step of information extraction comprises:

(2A) defining the video stream embedded with secret information receivedat an information extraction terminal as a target video stream andrecording the target video stream as str.bin_(dec); (2B) according tothe initial value information which generates the secret key E sent froman information embedding terminal, through the logistics chaoticmapping, generating a secret key E which is same as that of theinformation embedding terminal;

(2C) parsing the str.bin_(dec) frame by frame, and defining a frame tobe parsed in the str.bin_(dec) as a current frame;

(2D) judging the current frame is a P-frame or B -frame, wherein if itis, step (2E) is executed, otherwise, step (2H) is executed;

(2E) parsing the current frame coding-tree-unit by coding-tree-unit, anddefining a coding-tree-unit to be parsed in the current frame as acurrent parsing block;

(2F) judging whether the current parsing block is a skip block, whereinif it is, step (2G) is executed, otherwise, coding quantizationparameter embedded with secret information of the current parsing blockare parsed and recorded as QP′_(dec), and then a remainder result ofQP′_(dec) to 4 is calculated and recorded as d′_(dec), wherein thed′_(dec) is 0, 1, 2 or 3, and then the decimal d′_(dec) is transformedto binary number, values of two bits extracted from the current parsingblock are obtained, such that a secret information extraction process ofthe current parsing block is completed, and then the step (2G) isexecuted;

(2G) regarding a next coding-tree-unit to be parsed of the current frameas a current parsing block, and then returning to the step (2F) till allcoding-tree-units of the current frame are completely processed, andthen step (2H) is executed;

(2H) regarding a next frame to be parsed of the str.bin_(dec) as acurrent frame, and then returning to the step (2D) till all frames ofthe str.bin_(dec) are completely processed, such that secret informationextraction is completed; and (2I) defining extracted values of n_(W)bits as encrypted information and recording the encrypted information asW′_(dec), here, W′_(dec)=w′_(dec,n) _(W) w′_(dec,n) _(W) ₋₁ . . .w′_(dec,i) . . . w′_(dec,2) w′_(dec,1), and then perform an XOR(exclusive OR) operation on a value of each bit of the W_(dec) and avalue of each corresponding bit of the E, obtaining an XOR result,taking the XOR result as decrypt secret information and recording thedecrypt secret information as W_(dec) here, W_(dec)=w_(dec,n) _(W)w_(dec,n) _(W) ₋₁ . . . w_(dec,i) . . . w_(dec,2)w_(dec,1)wherein: thew′_(dec,n) _(W) w′_(dec,n) _(W) ₋₁ . . . w′_(dec,i) . . . w′_(dec,2)w′_(dec,1) respectively represent a value of the (n_(W))^(th) bit, avalue of the (n_(W)−1)^(th) bit, . . . , a value of the (i)^(th) bit, .. . a value of the second bit and a value of the first bit of theW′_(dec), each of the w′_(dec,n) _(W) w′_(dec,n) _(W) ₋₁ . . .w′_(dec,i) . . . w′_(dec,2) w′_(dec,1) is 0 or 1, w_(dec,n) _(W)w_(dec,n) _(W) ₋₁ . . . w_(dec,i) . . . w_(dec,2)w_(dec,1) respectivelyrepresent a value of the (n_(W))^(th) bit, a value of the (n_(W)−1)^(th)bit, . . . , a value of the (i)^(th) bit, . . . a value of the secondbit and a value of the first bit of the W_(dec), each of the w_(dec,n)_(W) w_(dec,n) _(W) ₋₁ . . . w_(dec,i) . . . w_(dec,2)w_(dec,1) is 0 or1.

In the step (1H-b) of the method, through the w′_(i′) and the w′_(i′+1),the QP_(org,j,k) is downwardly modulated to obtain the QP_(org,j,k),which is specifically embodied as: (b1) finding out all values in aninterval of [−3,QP_(org,j,k)] which meet a condition that a remainderresult of an absolute value of each of all the values to 4 is equal tod_(i′); (b2) calculating an absolute value of a difference value of eachof all the values found out in the step (b1) and the QP_(org,j,k); and(b3) finding out a minimum absolute value of all absolute valuescalculated in the step (b2), and assigning a value found out in the step(b1), which is corresponding to the minimum absolute value, to theQP′_(org,j,k).

In the step (1H-b) of the method, through the w′_(i′) and the w′_(i′+1),the QP_(org,j,k) is upwardly modulated to obtain the QP′_(org,j,k),which is specifically embodied as: (b1′) finding out all values in aninterval of [QP_(org,j,k),54] which meet a condition that a remainderresult of an absolute value of each of all the values to 4 is equal tod_(i′); (b2′) calculating an absolute value of a difference value ofeach of all the values found out in the step (b1′) and the QP_(org,j,k);and (b3′) finding out a minimum absolute value of all absolute valuescalculated in the step (b2′), and assigning a value found out in thestep (b1′), which is corresponding to the minimum absolute value, to theQP′_(org,j,k).

In the step (1H-c) of the method, through the w′_(i′) and the w′_(i′+1),the QP_(org,j,k) is downwardly modulated to regain the QP_(org,j,k),which is specifically embodied as: (c1) finding out all values in aninterval of [0,QP_(org,j,k)] which meet a condition that a remainderresult of an absolute value of each of all the values to 4 is equal tod_(i′); (c2) calculating an absolute value of a difference value of eachof all the values found out in the step (c1) and the QP_(org,j,k); and(c3) finding out a minimum absolute value of all absolute valuescalculated in the step (c2), and assigning a value found out in the step(c1), which is corresponding to the minimum absolute value, to theQP′_(org,j,k).

In the step (1H-c) of the method, through the w′_(i′) and the w′_(i′+1),the QP_(org,j,k) is upwardly modulated to regain the QP′_(org,j,k),which is specifically embodied as: (c1′) finding out all values in aninterval of [QP_(org,j,k),51] which meet a condition that a remainderresult of an absolute value of each of all the values to 4 is equal tod_(i′); (c2′) calculating an absolute value of a difference value ofeach of all the values found out in the step (c1′) and the QP_(org,j,k);and (c3′) finding out a minimum absolute value of all absolute valuescalculated in the step (c2′), and assigning a value found out in thestep (c1′), which is corresponding to the minimum absolute value, to theQP_(org,j,k).

Compared with the prior art, the present invention has advantages asfollows.

(1) When the present invention hides information in the 3D-HEVCcompressed domain, the human visual perception characteristic iscombined; the secret information is embedded under the guidance ofstereo saliency images, more bit rates are distributed in salient areas,less bit rates are distributed in non-salient areas, thus improving theperformance of the algorithm without obviously destroying human eyeviewing effects.

(2) The present invention is a stereo video information hiding methodfor inter-frames, and takes P-frames and B-frames as embedded frames toembed the secret information, which has little effect on the subjectivequality of stereoscopic videos.

(3) The present invention is different from the traditional videoinformation hiding methods which embed the secret information in theintra-frames, the DCT coefficients or the motion vectors. The embeddingvector selected by the present invention is a coding quantizationparameter, the secret information is embedded into the codingquantization parameter before coding, and then the coding quantizationparameter embedded with the secret information is used to encode thestereo video, so that no re-coding process is required, the phenomenonof error drift is avoided, and the computational complexity is low.

(4) The present invention builds the mapping relation between the secretinformation and the coding quantization parameter, and utilizes thesecret information to module the coding quantization parameter.Therefore, this modulation method is more flexible.

(5) The present invention does not need the participation of theoriginal video in the information extraction part and does not need totransmit any side information, the secret information can be blindly andeasily extracted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a general block diagram of an information embedding step of amethod provided by the present invention.

FIG. 1b is a general block diagram of an information extraction step ofthe method provided by the present invention.

FIG. 2a is a second frame of a second viewpoint of a stereo videosequence reconstructed from an encoded Newspaper stereo video streamwithout using a method provided by the present invention.

FIG. 2b is a second frame of a fourth viewpoint of a stereo videosequence reconstructed from an encoded Newspaper stereo video streamwithout using a method provided by the present invention.

FIG. 2c is a second frame of a first viewpoint of a stereo videosequence reconstructed from an encoded Shark stereo video stream withoutusing a method provided by the present invention.

FIG. 2d is a second frame of a ninth viewpoint of a stereo videosequence reconstructed from an encoded Shark stereo video stream withoutusing a method provided by the present invention.

FIG. 2e is a second frame of a second viewpoint of a stereo videosequence reconstructed from a Newspaper stereo video stream encodedthrough a method provided by the present invention.

FIG. 2f is a second frame of a fourth viewpoint of a stereo videosequence reconstructed from a Newspaper stereo video stream encodedthrough a method provided by the present invention.

FIG. 2g is a second frame of a first viewpoint of a stereo videosequence reconstructed from a Shark stereo video stream encoded througha method provided by the present invention.

FIG. 2h is a second frame of a ninth viewpoint of a stereo videosequence reconstructed from a Shark stereo video stream encoded througha method provided by the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is further explained in detail with accompanyingwith drawings and embodiments.

A 3D-HEVC inter-frame information hiding method based on visualperception, provided by the present invention, comprises steps ofinformation embedding and information extraction, wherein FIG. 1a showsa general block diagram of the step of information embedding which isspecifically embodied as:

(1A) at an information embedding terminal (for example an encoder ofstereo video signal), taking S_(org) as an original stereo video,recording a left view color video of the S_(org) as L_(org), recording aright view color video of the S_(org) as R_(org), and taking W as secretinformation to be embedded, wherein: W is a binary number which containsbits, W=w_(n) _(W) w_(n) _(W) ₋₁ . . . w_(i) . . . w₂w₁, a width of botha left view color image of the L_(org) and a right view color image ofthe R_(org) is M, a height thereof is N, both the M and the N can bedivisible by 64, a total frame number of both all left view color imagesof the L_(org) and all right view color images of the R_(org) is F,here, F≧1, n_(W) is a integer and

${n_{W} \in \left\lbrack {2,\frac{2 \times M \times N \times F}{64 \times 64}} \right\rbrack},$

w_(n) _(W) w_(n) _(W) ₋₁ . . . w_(i) . . . w₂w₁ respectively represent avalue of a (n_(W))^(th) bit, a value of a (n_(W)−1)^(th) bit, . . . , avalue of an i^(th) bit, . . . , a value of a second bit and a value of afirst bit, each of the w_(n) _(W) w_(n) _(W) ₋₁ . . . w_(i) . . . w₂w₁is 0 or 1, 1≦i≦n_(W);

(1B) obtaining a stereo saliency image of each left view color image ofthe L_(org) through an existing stereo image saliency model, recording astereo saliency image of a j^(th) left view color image of the L_(org)as P_(org,j) ^(u), calculating an otsu threshold of the stereo saliencyimage of each left view color image of the L_(org) and recording theotsu threshold of the L_(org,j) ^(u) as y_(j) ^(L), wherein 1≦j≦F,

also, obtaining a stereo saliency image of each right view color imageof the R_(org) through the existing stereo image saliency model,recording a stereo saliency image of a j^(th) right view color image ofthe R_(org) as R_(org,j) ^(u), calculating an otsu threshold of thestereo saliency image of each right view color image of the R_(org), andrecording the otsu threshold of the R_(org,j) ^(u) as y_(j) ^(R);

(1C) dividing the stereo saliency image of each left view color image ofthe L_(org) into non-overlapped

$\left( {\frac{M}{64} \times \frac{N}{64}} \right)$

image blocks each of which has a size of 64×64, recording a k^(th) imageblock of the L_(org,j) ^(u) as B_(org,j,k) ^(L), calculating a meanvalue of pixel values of all pixels of each image block of the stereosaliency image of each left view color image of the L_(org), recordingthe mean value of the pixel values of all the pixels of the B_(org,j,k)^(L) as q_(j,k) ^(L), determining whether each image block of the stereosaliency image of each left view color image of the L_(org) is a salientblock or a non-salient block according to the mean value of the pixelvalues of all the pixels of each image block of the stereo saliencyimage of each left view color image of the L_(org) and the otsuthreshold of the stereo saliency image of each left view color image ofthe L_(org) , wherein: if the q_(j,k) ^(L) is larger than or equal tothe y_(j) ^(L), the B_(org,j,k) ^(L) is determined to be the salientblock, if the q_(j,k) ^(L) is smaller than the y_(j) ^(L), theB_(org,j,k) ^(L) is determined to be the non-salient block, here,

${1 \leq k \leq {\frac{M}{64} \times \frac{N}{64}}},$

also, dividing the stereo saliency image of each right view color imageof the R_(org) into non-overlapped

$\left( {\frac{M}{64} \times \frac{N}{64}} \right)$

image blocks each of which has a size of 64×64, recording a k^(th) imageblock of the R_(org,j) ^(u) as B_(org,j,k) ^(R), calculating a meanvalue of pixel values of all pixels of each image block of the stereosaliency image of each right view color image of the R_(org), recordingthe mean value of the pixel values of all the pixels of the B_(org,j,k)^(R) as q_(j,k) ^(R), determining whether each image block of the stereosaliency image of each right view color image of the R_(org) is asalient block or a non-salient block according to the mean value of thepixel values of all the pixels of each image block of the stereosaliency image of each right view color image of the R_(org) and theotsu threshold of the stereo saliency image of each right view colorimage of the R_(org), wherein: if the q_(j,k) ^(R) is larger than orequal to the y_(j) ^(R), the B_(org,j,k) ^(R) is determined to be thesalient block, if the q_(j,k) ^(R) is smaller than the y_(j) ^(R), theB_(org,j,k) ^(R) is determined to be the non-salient block;

(1D) generating a binary pseudorandom sequence which contains n_(W) bitsthrough logistics chaotic mapping, taking the binary pseudorandomsequence as a secret key and recording the secret key as E, here,E=e_(n) _(W) e_(n) _(W) ₋₁ . . . e_(i) . . . e₂e₁, perform an XOR(exclusive OR) operation on a value of each bit of the W and a value ofeach corresponding bit of the E, obtaining an XOR result, taking the XORresult as encrypted information and recording the encrypted informationas W′, here, W′=w′_(n) _(W) w′_(n) _(W) ₋₁ . . . w′_(i) . . . w′₂ w′₁,wherein: the e_(n) _(W) e_(n) _(W) ₋₁ . . . e_(i) . . . e₂e₁respectively represent a value of the (n_(W))^(th) bit, a value of the(n_(W)1)^(th) bit, . . . , a value of the (i)^(th) bit, . . . a value ofthe second bit and a value of the first bit of the E, each of the e_(n)_(W) e_(n) _(W) ₋₁ . . . e_(i) . . . e₂e₁ is 0 or 1, w′_(n) _(W) w′_(n)_(W) ₋₁ . . . w′₂ w′₁ respectively represent a value of the (n_(W))^(th)bit, a value of the (n_(W)−1)^(th) bit, . . . , a value of the (i)^(th)bit, . . . a value of the second bit and a value of the first bit of theW′, each of the w′_(n) _(W) w′_(n) _(W) ₋₁ . . . w′_(i) . . . w′₂ w′₁ is0 or 1, w′_(i) is an XOR value of the w_(i) and the e_(i);

(1E) coding the L_(org) and the R_(org) in frame through a 3D-HEVCstandard coding platform, defining a j^(th) left view color image of theL_(org) to be coded or a j^(th) right view color image of the R_(org) tobe coded as a current frame and recording the current frame as P_(j)wherein an initial value of the j is 1,

while encoding the L_(org) and the B_(org), a 1^(st) left view colorimage of the L_(org) and a 1^(st) right view color image of the R_(org)are in turn, and so on, till a F^(th) left view color image of theL_(org) and a F^(th) right view color image of the R_(org) are encoded,and an entire encoding process is completed;

(1F) judging whether the P_(j) is a P-frame or a B-frame, wherein if itis, step (1G) is executed, if it is not, step (1I) is executed;

(1G) coding the P_(j) in coding-tree-unit (CTU), defining a k^(th)coding-tree-unit to be coded of the P_(j) as a current coding block andrecording the current coding block as B_(org,j,k), wherein

${1 \leq k \leq {\frac{M}{64} \times \frac{N}{64}}},$

here an initial value of the k is 1;

(1H-a) reading coding quantization parameter of the B_(org,j,k) andrecording the coding quantization parameter as QP_(org,j,k) reading avalue w′_(i′) of a i′^(th) bit of the W′ and a value w′_(i′+1) of a(i′+1)^(th) bit of the W′, transforming the w′_(i′+1) and the w′_(i′)into decimal value and recording the decimal values as d_(i′), here,

$d_{i^{\prime}} = \left\{ {\begin{matrix}0 & {{w_{i^{\prime} + 1}^{\prime}w_{i^{\prime}}^{\prime}} = 00} \\1 & {{w_{i^{\prime} + 1}^{\prime}w_{i^{\prime}}^{\prime}} = 01} \\2 & {{w_{i^{\prime} + 1}^{\prime}w_{i^{\prime}}^{\prime}} = 10} \\3 & {{w_{i^{\prime} + 1}^{\prime}w_{i^{\prime}}^{\prime}} = 11}\end{matrix},} \right.$

wherein an initial value of the i′ is 1, 1≦i′≦n_(W)−1, and each ofw′_(i′) and w′_(i′+1) is 0 or 1;

(1H-b) when the P_(j) is the j^(th) left view color image of theL_(org), judging whether a remainder result of the QP_(org,j,k) to 4 isequal to the d_(i′), wherein if the remainder result is not equal to thed_(i′), when the B_(org,j,k) ^(L) is a salient block, the QP_(org,j,k)is downwardly modulated by the w′_(i′) and the w′_(i′+1), so that codingquantization parameter embedded with secret information of theB_(org,j,k) is obtained and recorded as QP′_(org,j,k), and then step(1H-c) is executed; when the B_(org,j,k) ^(L) is a non-salient block,the QP_(org,j,k) is upwardly modulated by the w′_(i′) and the w′_(i′+1),so that the coding quantization parameter embedded with secretinformation of the B_(org,j,k k) is obtained and recorded as theQP′_(org,j,k), and then the step (1H-c) is executed; if the remainderresult is equal to the d_(i′), the QP_(org,j,k) is directly recorded asthe coding quantization parameter embedded with secret information ofthe B_(org,j,k) which is denoted as the QP′_(org,j,k),QP′_(org,j,k)=QP_(org,j,k), and then the step (1H-c) is executed, here,“=” is an assignment symbol in the QP′_(org,j,k)=QP_(org,j,k);

when the P_(j) is the j^(th) right view color image of the R_(org),judging whether a remainder result of the QP_(org,j,k) to 4 is equal tothe d_(i′), wherein if the remainder result is not equal to the d_(i′),when the B_(org,j,k) ^(R) is a salient block, the QP_(org,j,k)downwardly modulated by the w′_(i′) and the w′_(i′+1), so that codingquantization parameter embedded with secret information of theB_(org,j,k) is obtained and recorded as QP′_(org,j,k), and then the step(1H-c) is executed; when the B_(org,j,k) ^(R) is a non-salient block,the QP_(org,j,k) upwardly modulated by the w′_(i′) and the w′_(i′+1), sothat the coding quantization parameter embedded with secret informationof the B_(org,j,k) is obtained and recorded as the QP′_(org,j,k), andthen the step (1H-c) is executed; if the remainder result is equal tothe d_(i′), the QP_(org,j,k) is directly recorded as the codingquantization parameter embedded with secret information of theB_(org,j,k) which is denoted as the QP′_(org,j,k),QP′_(org,j,k)=QP_(org,j,k), and then the step (1H-c) is executed;

(1H-c) judging whether the QP′_(org,j,k) is in a range of [0, 51],wherein if it is, step (1H-d) is executed; otherwise, whenQP′_(org,j,k)>51, the QP_(org,j,k) is downwardly modulated by thew′_(i′) and the w′_(i′+1) the coding quantization parameter embeddedwith secret information QP′_(org,j,k) of the B_(org,j,k) is obtainedagain, and then the step (1H-d) is executed; when QP′_(org,j,k)<0, theQP_(org,j,k) is upwardly modulated by the w′_(i′) and the w′_(i′+1), thecoding quantization parameter embedded with secret informationQP′_(org,j,k) of the B_(org,j,k) is obtained again, and then the step(1H-d) is executed;

(1H-d) coding the B_(org,j,k) with the QP′_(org,j,k), completing asecret information embedded process of the B_(org,j,k), after completingcoding of the B_(org,j,k), judging whether the B_(org,j,k) is a skipblock, wherein if it is, step (1H-e) is directly executed, otherwise,i′=i′+2 is set, the step (1H-e) is executed, here, “=” is an assignmentsymbol in the i′=i′+2;

(1H-e) setting k=k+1, regarding a next coding-tree-unit to be coded ofthe P_(j) as a current coding block and recording the nextcoding-tree-unit to be coded as B_(org,j,k), returning to the step(1H-a) to continue till all coding-tree-units of the P_(j) arecompletely coded, executing step (1I), wherein “=” is an assignmentsymbol in the k=k+1;

(1I) setting j=j+1, regarding a next left view color image to be codedof the L_(org) or a next right view color image to be coded of theR_(org) as a current frame and recording the current frame as P_(j),returning to the step (1F) and continuing till all left view colorimages in the L_(org) and all right view color images in the R_(org) arecompletely coded, and obtaining video stream embedded with secretinformation, wherein “=” is an assignment symbol in the j=j+1; and

(1J) sending initial value information which generates the secret key Eto an information extraction terminal.

FIG. 1b shows a general block diagram of the step of informationextraction, which is specifically embodied as:

(2A) defining the video stream embedded with secret information receivedat an information extraction terminal (for example, a decoder of stereovideo signal) as a target video stream and recording the target videostream as str.bin_(dec); (2B) according to the initial value informationwhich generates the secret key E sent from an information embeddingterminal, through the logistics chaotic mapping, generating a secret keyE which is same as that of the information embedding terminal, whereinif the secret key E is directly transmitted to the informationextraction terminal, then side information is too big, due to theprocess of generating the secret key is relatively simple, the secretkey can be reproduced only by giving an initial value, and therefore,based on the initial value information which generates the secret key Esent from the information embedding terminal, it is only necessary tore-generate for obtaining the secret key at the information extractionterminal as same as the secret key at the information embeddingterminal;

(2C) parsing the str.bin_(dec) frame by frame, and defining a frame tobe parsed in the str.bin_(dec) as a current frame;

(2D) judging the current frame is a P-frame or B-frame, wherein if itis, step (2E) is executed, otherwise, step (2H) is executed;

(2E) parsing the current frame coding-tree-unit (CTU) bycoding-tree-unit, and defining a coding-tree-unit to be parsed in thecurrent frame as a current parsing block;

(2F) judging whether the current parsing block is a skip block, whereinif it is, step (2G) is executed, otherwise, coding quantizationparameter embedded with secret information of the current parsing blockare parsed and recorded as QP′_(dec), and then a remainder result ofQP′_(dec) to 4 is calculated and recorded as d′_(dec), wherein thed′_(dec) is 0, 1, 2 or 3, and then the decimal d′_(dec) is transformedto binary number, values of two bits extracted from the current parsingblock are obtained, such that a secret information extraction process ofthe current parsing block is completed, and then the step (2G) isexecuted;

(2G) regarding a next coding-tree-unit to be parsed of the current frameas a current parsing block, and then returning to the step (2F) till allcoding-tree-units of the current frame are completely processed, andthen step (2H) is executed;

(2H) regarding a next frame to be parsed of the str.bin_(dec) as acurrent frame, and then returning to the step (2D) till all frames ofthe str.bin_(dec) are completely processed, such that secret informationextraction is completed; and (21) defining extracted values of n_(W)bits as encrypted information and recording the encrypted information asW′_(dec), here, W′_(dec)=w′_(dec,n) _(W) w′_(dec,n) _(W) ₋₁ . . .w′_(dec,i) . . . w′_(dec,2) w′_(dec,1), and then perform an XOR(exclusive OR) operation on a value of each bit of the W′_(dec) and avalue of each corresponding bit of the E, obtaining an XOR result,taking the XOR result as decrypt secret information and recording thedecrypt secret information as W_(dec), here, W_(dec)=w_(dec,n) _(W)w_(dec,n) _(W) ₋₁ . . . w_(dec,i) . . . w_(dec,2)w_(dec,1), wherein: thew′_(dec,n) _(W) w′_(dec,n) _(W) ₋₁ . . . w′_(dec,i) . . . w′_(dec,2)w′_(dec,1), respectively represent a value of the (n_(W))^(th) bit, avalue of the (n_(W)−1)^(th) bit, . . . , a value of the (i)^(th) bit, .. . a value of the second bit and a value of the first bit of theW′_(dec), each of the w′_(dec,n) _(W) w′_(dec,n) _(W) ₋₁ . . .w′_(dec,i) . . . w′_(dec,2) w′_(dec,1) is 0 or 1, w_(dec,n) _(W)w_(dec,n) _(W) ₋₁ . . . w_(dec,i) . . . w_(dec,2)w_(dec,1) respectivelyrepresent a value of the (n_(W))^(th) bit, a value of the (n_(W)−1)^(th)bit, . . . , a value of the (i)^(th) bit, . . . a value of the secondbit and a value of the first bit of the W_(dec), each of the w_(dec,n)_(W) w_(dec,n) _(W) ₋₁ . . . w_(dec,i) . . . w_(dec,2)w_(dec,1) is 0 or1.

In the step (1H-b) of the method according to this specific embodiment,through the w′_(i′), and the w′_(i′+1), the QP_(org,j,k) is downwardlymodulated to obtain the QP′_(org,j,k), which is specifically embodiedas: (b1) finding out all values in an interval of [−3,QP_(org,j,k)]which meet a condition that a remainder result of an absolute value ofeach of all the values to 4 is equal to d_(i′); (b2) calculating anabsolute value of a difference value of each of all the values found outin the step (b1) and the QP_(org,j,k); and (b3) finding out a minimumabsolute value of all absolute values calculated in the step (b2), andassigning a value found out in the step (b1), which is corresponding tothe minimum absolute value, to the QP′_(org,j,k), that is, QP_(org,j,k)meets a condition of

$\left\{ {\begin{matrix}{{QP}_{{org},j,k}^{\prime} \in \left\lbrack {{- 3},{QP}_{{org},j,k}} \right\rbrack} \\{{{{QP}_{{org},j,k}^{\prime}}{mod}\; 4} = d_{i^{\prime}}} \\{\min \left( {{{QP}_{{org},j,k}^{\prime} - {QP}_{{org},j,k}}} \right)}\end{matrix},} \right.$

wherein mod is a mathematical symbol for taking a remainder, and min( )is a function for taking a minimum.

In the step (1H-b) of the method according to this specific embodiment,through the w′_(i′) and the w′_(i′+1), the QP_(org,j,k) is upwardlymodulated to obtain the QP′_(org,j,k), which is specifically embodiedas: (b1′) finding out all values in an interval of [QP_(org,j,k),54]which meet a condition that a remainder result of an absolute value ofeach of all the values to 4 is equal to d_(i′); (b2′) calculating anabsolute value of a difference value of each of all the values found outin the step (b1′) and the QP_(org,j,k); and (b3′) finding out a minimumabsolute value of all absolute values calculated in the step (b2′), andassigning a value found out in the step (b1′), which is corresponding tothe minimum absolute value, to the QP′_(org,j,k), that is, QP′_(org,j,k)meets a condition of

$\left\{ {\begin{matrix}{{QP}_{{org},j,k}^{\prime} \in \left\lbrack {{QP}_{{org},j,k},54} \right\rbrack} \\{{{QP}_{{org},j,k}^{\prime}\mspace{11mu} {mod}\; 4} = d_{i^{\prime}}} \\{\min \left( {{{QP}_{{org},j,k}^{\prime} - {QP}_{{org},j,k}}} \right)}\end{matrix}.} \right.$

In the step (1H-c) of the method according to this specific embodiment,through the w′_(i), and the w′_(i′+1), the QP_(org,j,k) is downwardlymodulated to regain the QP′_(org,j,k), which is specifically embodiedas: (c1) finding out all values in an interval of [0,QP_(org,j,k)] whichmeet a condition that a remainder result of an absolute value of each ofall the values to 4 is equal to d_(i′); (c2) calculating an absolutevalue of a difference value of each of all the values found out in thestep (c1) and the QP_(org,j,k); and (c3) finding out a minimum absolutevalue of all absolute values calculated in the step (c2), and assigninga value found out in the step (c1), which is corresponding to theminimum absolute value, to the QP′_(org,j,k), that is, QP′_(org,j,k)meets a condition of

$\left\{ {\begin{matrix}{{QP}_{{org},j,k}^{\prime} \in \left\lbrack {0,{QP}_{{org},j,k}} \right\rbrack} \\{{{QP}_{{org},j,k}^{\prime}\mspace{11mu} {mod}\; 4} = d_{i^{\prime}}} \\{\min \left( {{{QP}_{{org},j,k}^{\prime} - {QP}_{{org},j,k}}} \right)}\end{matrix}.} \right.$

In the step (1H-c) of the method according to this specific embodiment,through the w′_(i′) and the w′_(i′+1), the QP_(org,j,k) is upwardlymodulated to regain the QP′_(org,j,k), which is specifically embodiedas: (c1′) finding out all values in an interval of [QP_(org,j,k),51]which meet a condition that a remainder result of an absolute value ofeach of all the values to 4 is equal to d_(i′); (c2′) calculating anabsolute value of a difference value of each of all the values found outin the step (c1′) and the QP_(org,j,k); and (c3′) finding out a minimumabsolute value of all absolute values calculated in the step (c2′), andassigning a value found out in the step (c1′), which is corresponding tothe minimum absolute value, to the QP′_(org,j,k) that is, QP′_(org,j,k)meets a condition of

$\left\{ {\begin{matrix}{{QP}_{{org},j,k}^{\prime} \in \left\lbrack {{QP}_{{org},j,k},51} \right\rbrack} \\{{{QP}_{{org},j,k}^{\prime}{mod}\; 4} = d_{i^{\prime}}} \\{\min \left( {{{QP}_{{org},j,k}^{\prime} - {QP}_{{org},j,k}}} \right)}\end{matrix}.} \right.$

In order to verify the effectiveness and the feasibility of the methodprovided by the present invention, the method provided by the presentinvention is tested.

Adopted test sequences are as follows: a 3^(rd) and 5^(th) viewpoint ofa Balloons stereo video sequence, a 2^(nd) and 4^(th) viewpoint of aNewspaper stereo video sequence, a 1^(st) and 9^(th) viewpoint of aShark stereo video sequence and a 1^(st) and 9^(th) viewpoint of aUndoDancer stereo video sequence. A resolution of the former two stereovideo sequences is 1024×768, and a resolution of the latter two stereovideo sequences is 1920×1088. Test software is a coding platform HTM13.0based on 3D-HEVC standard which codes 100 frames under random access,given target bit rates are respectively 2000, 4000, 5000 and 6000 kbps,and other configuration parameters are platform defaults. Theperformance of the method provided by the present invention will berespectively evaluated from the imperceptibility, the embedding capacityand the bit rate change of the stereo video sequence.

1) The Imperceptibility of the Stereo Video Sequence

To verify the effect of the method provided by the present invention onthe subjective quality of the stereo video sequence, here, the Newspaperstereo video sequence and the Shark stereo video sequence are selectedto explain. FIG. 2a is a second frame of a second viewpoint of a stereovideo sequence reconstructed from an encoded Newspaper stereo videostream without using the method provided by the present invention. FIG.2b is a second frame of a fourth viewpoint of a stereo video sequencereconstruceted from an encoded Newspaper stereo video stream withoutusing the method provided by the present invention. FIG. 2c is a secondframe of a first viewpoint of a stereo video sequence reconstrucetedfrom an encoded Shark stereo video stream without using the methodprovided by the present invention. FIG. 2d is a second frame of a ninthviewpoint of a stereo video sequence reconstruceted from an encodedShark stereo video stream without using the method provided by thepresent invention. In other words, the frames in FIG. 2a , FIG. 2b ,FIG. 2c and FIG. 2d are normally encoded through the coding platformHTM13.0 based on 3D-HEVC standard, therefore, these frames do notcontain any secret information. By contrast, FIG. 2e is a second frameof a second viewpoint of a stereo video sequence reconstructed from aNewspaper stereo video stream encoded through a method provided by thepresent invention. FIG. 2f is a second frame of a fourth viewpoint of astereo video sequence reconstructed from a Newspaper stereo video streamencoded through a method provided by the present invention. FIG. 2g is asecond frame of a first viewpoint of a stereo video sequencereconstructed from a Shark stereo video stream encoded through a methodprovided by the present invention. FIG. 2h is a second frame of a ninthviewpoint of a stereo video sequence reconstructed from a Shark stereovideo stream encoded through a method provided by the present invention.That is to say, the frames in FIG. 2e , FIG. 2f , FIG. 2g and FIG. 2hhave been embedded in secret information. Compared FIG. 2a with FIG. 2e, FIG. 2b with FIG. 2f , FIG. 2c with FIG. 2g , and FIG. 2d with FIG. 2h, it can be seen that after secret information is embedded, the qualityof the viewpoint of the stereo video sequence is not obviouslydistorted, which shows that the method provided by the present inventionhas a better stereo video imperceptibility.

To further evaluate the quality of the stereo video sequence, arepresentative index such as PSNR (peak signal-to-noise ratio) isintroduced into the experiment to explain. Table 1 shows the quality ofthe stereo video sequences which are respectively obtained by performingnormal encoding on an original Balloons stereo video sequence, anoriginal Newspaper stereo video sequence, an original Shark stereo videosequence and an original UndoDancer stereo video sequence, and thendecoding the encoded video stream, and also shows the quality of thestereo video sequences which are respectively obtained by performingencoding on an original Balloons stereo video sequence, an originalNewspaper stereo video sequence, an original Shark stereo video sequenceand an original UndoDancer stereo video sequence through the methodprovided by the present invention, and then decoding the encoded videostream. A computational formula of a variation ΔPSNR of the PSNR beforeand after inserting the secret information isΔPSNR=PSNR_(pro)−PSNR_(org), wherein the PSNR_(pro) represent a meanPSNR of two viewpoints of the stereo video sequence obtained byperforming encoding on an original stereo video sequence through themethod provided by the present invention, and then decoding the encodedvideo stream, and PSNR_(org) represents a mean PSNR of two viewpoints ofthe stereo video sequence obtained by performing normal encoding on anoriginal stereo video sequence, and then decoding the encoded videostream. In this experiment, the imperceptibility of the stereo videosequence is explained through the ΔPSNR.

It can be seen from Table 1 that after being performed the encoding atdifferent target bit rates, the stereo video sequence has differentqualities. The reason is that the smaller the given target bit rate, theless the bits allocated to the viewpoint, the poor the quality of thereconstructed stereo video sequence. Simultaneously, in Table 1, theabsolute value of ΔPSNR is in a range of 0.0014-0.0524 dB, and theaverage of ΔPSNR is −0.03139 dB, which shows that the method provided bythe present invention has a slight impact on the quality of the encodedstereo video sequence. The method provided by the present inventioncombines with the stereo image salient model to guide the embedding ofthe secret information, and only finely tunes the coding quantizationparameters, so that the method provided by the present invention has asmaller impact on the quality of the stereo video sequence.

TABLE 1 The impact of the method provided by the present invention onthe quality of encoded stereo video sequences Stereo video Target bitPSNR (dB) sequence Resolution rate PSNR_(org) PSNR_(pro) ΔPSNR Balloons1024 × 768  2000 43.3970 43.3490 −0.0480 4000 44.5928 44.5620 −0.03085000 44.9503 44.9126 −0.0377 6000 45.2222 45.1847 −0.0375 Newspaper 1024× 768  2000 41.8957 41.8433 −0.0524 4000 43.7668 43.7223 −0.0445 500044.2632 44.2175 −0.0457 6000 44.7029 44.6653 −0.0376 Shark 1920 × 10882000 35.2779 35.2452 −0.0327 4000 38.3170 38.3011 −0.0159 5000 39.316239.2982 −0.0180 6000 40.1200 40.0972 −0.0228 UndoDancer 1920 × 1088 200034.2069 34.1915 −0.0154 4000 36.4754 36.4579 −0.0175 5000 37.166737.1681 0.0014 6000 37.7911 37.7440 −0.0471

2) Embedded Capacity and Bit Rate Change of the Stereo Video Sequence

Generally speaking, in the encoding process of the stereo videosequence, embedding the secret information through the codingquantization parameters causes a change in the coding bit rate. Table 2shows test results of the embedded capacity and the bit rate change ofthe Balloons stereo video sequence, the Newspaper stereo video sequence,the Shark stereo video sequence and the UndoDancer stereo video sequencethrough the method provided by the present invention. In Table 2, theembedded capacity is a total sum of the embedded capacities of thestereo video sequences, and the bit rate change is defined as

${{B\; R\; I} = {\frac{R_{pro} - R_{org}}{R_{org}} \times 100\%}},$

here, the R_(pro) represents a bit rate of an original stereo videosequence after being processed through the method provided by thepresent invention and then performed the compression coding, and theR_(org) represents a bit rate of an original stereo video sequence afterbeing performed the compression coding.

It can be seen from Table 2 that with the increase of the resolution ofthe stereo video sequence, the embedded capacity is increased, thereason is that the greater the resolution, the more the allocatedcoding-tree-units, the more the embedded vectors. An average embeddedcapacity of the stereo video sequence at different target bit rates is47236 bits, and the bit rate is average increased by 0.0741%, whichshows that the method provided by the present invention can provide highembedded capacity and has less effect on the bit rate of the coding, dueto the method provided by the present invention finely tunes the codingquantization parameters, simultaneously starts the bit rate controlmodule to effectively restrain the change of the bit rate.

TABLE 2 Test results of the embedded capacity and the bit rate change ofthe method provided by the present invention Target Embedded Bit rate(kbps) Stereo video bit capacity Original Present Change sequenceResolution rate (bit) coding invention rate Balloons 1024 × 768  200033760 2036.950 2036.928 −0.0011% 4000 46058 4013.657 4013.998 0.0085%5000 52696 5004.686 5005.380 0.0139% 6000 56538 6004.975 6005.5560.0097% Newspaper 1024 × 768  2000 26772 2048.866 2049.118 0.0123% 400038038 4056.552 4057.445 0.0220% 5000 44332 5048.395 5048.206 −0.0037%6000 49170 6027.574 6027.962 0.0064% Shark 1920 × 1088 2000 408642002.462 2002.202 −0.0130% 4000 56782 4010.378 4012.063 0.0420% 500063356 5008.946 5012.633 0.0736% 6000 69100 6007.138 6006.845 −0.0049%UndoDancer 1920 × 1088 2000 29438 2016.056 2014.082 −0.0979% 4000 435884074.594 4104.764 0.7404% 5000 49358 5063.886 5098.290 0.6794% 600055924 6120.974 6102.510 −0.3017%

One skilled in the art will understand that the embodiment of thepresent invention as shown in the drawings and described above isexemplary only and not intended to be limiting.

It will thus be seen that the objects of the present invention have beenfully and effectively accomplished. Its embodiments have been shown anddescribed for the purposes of illustrating the functional and structuralprinciples of the present invention and is subject to change withoutdeparture from such principles. Therefore, this invention includes allmodifications encompassed within the spirit and scope of the followingclaims.

What is claimed is:
 1. A 3D-HEVC (Three Dimensional High EfficiencyVideo Coding) inter-frame information hiding method based on visualperception comprising steps of information embedding and informationextraction, wherein: the step of information embedding comprises: (1A)at an information embedding terminal, taking S_(org) as an originalstereo video, recording a left view color video of the S_(org) asL_(org), recording a right view color video of the S_(org) as R_(org),and taking W as secret information to be embedded, wherein: W is abinary number which contains n_(W) bits, W=w_(n) _(W) w_(n) _(W) ₋₁ . .. w_(i) . . . w₂w₁, a width of both a left view color image of theL_(org) and a right view color image of the R_(org) is M, a heightthereof is N, both the M and the N can be divisible by 64, a total framenumber of both all left view color images of the L_(org) and all rightview color images of the R_(org) is F, here, F≧1, is a integer and${n_{W} \in \left\lbrack {2,\frac{2 \times M \times N \times F}{64 \times 64}} \right\rbrack},$w_(n) _(W) w_(n) _(W) ₋₁ . . . w_(i) . . . w₂w₁ respectively represent avalue of (n_(W))^(th) bit, a value of a (n_(W)−1)^(th) bit, . . . , avalue of an i^(th) bit, a value of a second bit and a value of a firstbit, each of the w_(n) _(W) w_(n) _(W) ⁻¹ . . . w_(i) . . . w₂w₁ is 0 or1, 1≦i≦n_(W); (1B) obtaining a stereo saliency image of each left viewcolor image of the L_(org) through a stereo image saliency model,recording a stereo saliency image of a j^(th) left view color image ofthe L_(org) as L_(org,j) ^(u), calculating an otsu threshold of thestereo saliency image of each left view color image of the L_(org), andrecording the otsu threshold of the L_(org,j) ^(u) as y_(j) ^(L),wherein 1≦j≦F, also, obtaining a stereo saliency image of each rightview color image of the R_(org) through the stereo image saliency model,recording a stereo saliency image of a j^(th) right view color image ofthe R_(org) as R_(org,j,) ^(u), calculating an otsu threshold of thestereo saliency image of each right view color image of the R_(org), andrecording the otsu threshold of the R_(org,j) ^(u) as y_(j) ^(R); (1C)dividing the stereo saliency image of each left view color image of theL_(org) into non-overlapped$\left( {\frac{M}{64} \times \frac{N}{64}} \right)$ image blocks each ofwhich has a size of 64×64, recording a k^(th) image block of theL_(org,j) ^(u) as B_(org,j,k) ^(L), calculating a mean value of pixelvalues of all pixels of each image block of the stereo saliency image ofeach left view color image of the L_(org) recording the mean value ofthe pixel values of all the pixels of the B_(org,j,k) ^(L) as q_(j,k)^(L), determining whether each image block of the stereo saliency imageof each left view color image of the L_(org) is a salient block or anon-salient block according to the mean value of the pixel values of allthe pixels of each image block of the stereo saliency image of each leftview color image of the L_(org) and the otsu threshold of the stereosaliency image of each left view color image of the L_(org), wherein: ifthe q_(j,k) ^(L) is larger than or equal to the y_(j) ^(L), theB_(org,j,k) ^(L) is determined to be the salient block, if the q_(j,k)^(L) is smaller than the y_(j) ^(L), the B_(org,j,k) ^(L) is determinedto be the non-salient block, here,${1 \leq k \leq {\frac{M}{64} \times \frac{N}{64}}},$ also, dividing thestereo saliency image of each right view color image of the R_(org) intonon-overlapped $\left( {\frac{M}{64} \times \frac{N}{64}} \right)$ imageblocks each of which has a size of 64×64, recording a k^(th) image blockof the R_(org,j) ^(u) as R_(org,j,k) ^(R), calculating a mean value ofpixel values of all pixels of each image block of the stereo saliencyimage of each right view color image of the R_(org), recording the meanvalue of the pixel values of all the pixels of the B_(org,j,k) ^(R) asq_(j,k) ^(R), determining whether each image block of the stereosaliency image of each right view color image of the R_(org) is asalient block or a non-salient block according to the mean value of thepixel values of all the pixels of each image block of the stereosaliency image of each right view color image of the R_(org) and theotsu threshold of the stereo saliency image of each right view colorimage of the R_(org), wherein: if the q_(j,k) ^(R) is larger than orequal to the y_(j) ^(R), the B_(org,j,k) ^(R) is determined to be thesalient block, if the q_(j,k) ^(R) is smaller than the y_(j) ^(R), theB_(org,j,k) ^(R) is determined to be the non-salient block; (1D)generating a binary pseudorandom sequence which contains n_(W) bitsthrough logistics chaotic mapping, taking the binary pseudorandomsequence as a secret key and recording the secret key as E, here,E=e_(n) _(W) e_(n) _(W) ₋₁ . . . e_(i) . . . e₂e₁, perform an XOR(exclusive OR) operation on a value of each bit of the W and a value ofeach corresponding bit of the E, obtaining an XOR result, taking the XORresult as encrypted information and recording the encrypted informationas W′, here, W′=w′_(n) _(W) w′_(n) _(W) ₋₁ . . . w′_(i) . . . w′₂ w′₁,wherein: the e_(n) _(W) e_(n) _(W) ₋₁ . . . e_(i) . . . e₂e₁respectively represent a value of the (n_(W))^(th) bit, a value of the(n_(W)−1)^(th) bit, . . . , a value of the (i)^(th) bit, . . . a valueof the second bit and a value of the first bit of the E, each of thee_(n) _(W) e_(n) _(W) ₋₁ . . . e_(i) . . . e₂e₁ is 0 or 1, w′_(n) _(W)w′_(n) _(W) ₋₁ . . . w′_(i) . . . w′₂ w′₁ respectively represent a valueof the (n_(W))^(th) bit, a value of the (n_(W)−1)^(th) bit, . . . , avalue of the (i)^(th) bit, . . . a value of the second bit and a valueof the first bit of the W′, each of the w′_(n) _(W) w′_(n) _(W) ₋₁ . . .w′_(i) . . . w′₂ w′₁ is 0 or 1, w is an XOR value of the w_(i) and thee_(i); (1E) coding the L_(org) and the R_(org) in frame through a3D-HEVC standard coding platform, defining a j^(th) left view colorimage of the L_(org) to be coded or a j^(th) right view color image ofthe R_(org) to be coded as a current frame and recording the currentframe as P_(j), wherein an initial value of the j is 1; (1F) judgingwhether the P_(j) is a P-frame or a B-frame, wherein if it is, step (1G)is executed, if it is not, step (11) is executed; (1G) coding the P_(j)in coding-tree-unit, defining a k^(th) coding-tree-unit to be coded ofthe P_(j) as a current coding block and recording the current codingblock as B_(org,j,k), wherein${1 \leq k \leq {\frac{M}{64} \times \frac{N}{64}}},$ here an initialvalue of the k is 1; (1H-a) reading coding quantization parameter of theB_(org,j,k) and recording the coding quantization parameter asQP_(org,j,k), reading a value w′_(i′) of a i′^(th) bit of the W′ and avalue w′_(i′+1) of a (i′+1)^(th) bit of the W′, transforming thew′_(i′+1) and the w′_(i′) into decimal values and recording the decimalvalue as d_(i′), here, $d_{i^{\prime}} = \left\{ {\begin{matrix}0 & {{w_{i^{\prime} + 1}^{\prime}w_{i^{\prime}}^{\prime}} = 00} \\1 & {{w_{i^{\prime} + 1}^{\prime}w_{i^{\prime}}^{\prime}} = 01} \\2 & {{w_{i^{\prime} + 1}^{\prime}w_{i^{\prime}}^{\prime}} = 10} \\3 & {{w_{i^{\prime} + 1}^{\prime}w_{i^{\prime}}^{\prime}} = 11}\end{matrix},} \right.$ wherein an initial value of the i′ is 1,1≦i′≦n_(W)−1, and each of w′_(i′) and w′_(i′+1) is 0 or 1; (1H-b) whenthe P_(j) is the j^(th) left view color image of the L_(org), judgingwhether a remainder result of the QP_(org,j,k) to 4 is equal to thed_(i′), wherein if the remainder result is not equal to the d_(i′), whenthe B_(org,j,k) ^(L) is a salient block, the QP_(org,j,k) is downwardlymodulated by the w′_(i′) and the w′_(i′+1), so that coding quantizationparameter embedded with secret information of the B_(org,j,k) isobtained and recorded as QP′_(org,j,k), and then step (1H-c) isexecuted; when the B_(org,j,k) ^(L) is a non-salient block, theQP_(org,j,k) is upwardly modulated by the w′_(i′) and the w′_(i′+1), sothat the coding quantization parameter embedded with secret informationof the B_(org,j,k) is obtained and recorded as the QP′_(org,j,k), andthen the step (1H-c) is executed; if the remainder result is equal tothe d_(i′), the QP_(org,j,k) is directly recorded as the codingquantization parameter embedded with secret information of theB_(org,j,k) which is denoted as the QP′_(org,j,k),QP′_(org,j,k)=QP_(org,j,k), and then the step (1H-c) is executed, here,“=” is an assignment symbol in the QP′_(org,j,k)=QP_(org,j,k); when theP_(j) is the j^(th) right view color image of the R_(org), judgingwhether a remainder result of the QP_(org,j,k) to 4 is equal to thed_(i′), wherein if the remainder result is not equal to the d_(i′), whenthe B_(org,j,k) ^(R) is a salient block, the QP_(org,j,k) is downwardlymodulated by the w′_(i′) and the w′_(i′+1), so that coding quantizationparameter embedded with secret information of the B_(org,j,k) isobtained and recorded as QP′_(org,j,k), and then the step (1H-c) isexecuted; when the B_(org,j,k) ^(R) is a non-salient block, theQP_(org,j,k) is upwardly modulated by the w′_(i′) and the w′_(i′+1), sothat the coding quantization parameter embedded with secret informationof the B_(org,j,k) is obtained and recorded as the QP′_(org,j,k), andthen the step (1H-c) is executed; if the remainder result is equal tothe d_(i′), the QP_(org,j,k) is directly recorded as the codingquantization parameter embedded with secret information of theB_(org,j,k) which is denoted as the QP′_(org,j,k),QP′_(org,j,k)=QP_(org,j,k), and then the step (1H-c) is executed; (1H-c)judging whether the QP′_(org,j,k) is in a range of [0, 51], wherein ifit is, step (1H-d) is executed; otherwise, when QP′_(org,j,k)>51, theQP_(org,j,k) is downwardly modulated by the w′_(i′) and the w′_(i′+1),the coding quantization parameter embedded with secret informationQP′_(org,j,k) of the B_(org,j,k) is obtained again, and then the step(1H-d) is executed; when QP′_(org,j,k)<0, the QP_(org,j,k) is upwardlymodulated by the w′_(i′) and the w′_(i′+1), the coding quantizationparameter embedded with secret information QP′_(org,j,k) of theB_(org,j,k) is obtained again, and then the step (1H-d) is executed;(1H-d) coding the B_(org,j,k) with the QP′_(org,j,k), completing asecret information embedded process of the B_(org,j,k), after completingcoding of the B_(org,j,k), judging whether the B_(org,j,k) is a skipblock, wherein if it is, step (1H-e) is directly executed, otherwise,i′=i′+2 is set, the step (1H-e) is executed, here, “=” is an assignmentsymbol in the i′=i′+2; (1H-e) setting k=k+1, regarding a nextcoding-tree-unit to be coded of the P_(j) as a current coding block andrecording the next coding-tree-unit to be coded as B_(org,j,k),returning to the step (1H-a) to continue till all coding-tree-units ofthe P_(j) are completely coded, executing step (1I), wherein “=” is anassignment symbol in the k=k+1; (11) setting j=j+1, regarding a nextleft view color image to be coded of the L_(org) or a next right viewcolor image to be coded of the R_(org) as a current frame and recordingthe current frame as P_(j), returning to the step (1F) and continuingtill all left view color images in the L_(org) and all right view colorimages in the R_(org) are completely coded, and obtaining video streamembedded with secret information, wherein “=” is an assignment symbol inthe j=j+1; and (1J) sending initial value information which generatesthe secret key E to an information extraction terminal; the step ofinformation extraction comprises: (2A) defining the video streamembedded with secret information received at an information extractionterminal as a target video stream and recording the target video streamas str.bin_(dec); (2B) according to the initial value information whichgenerates the secret key E sent from an information embedding terminal,through the logistics chaotic mapping, generating a secret key E whichis same as that of the information embedding terminal; (2C) parsing thestr.bin_(dec) frame by frame, and defining a frame to be parsed in thestr.bin_(dec) as a current frame; (2D) judging the current frame is aP-frame or B-frame, wherein if it is, step (2E) is executed, otherwise,step (2H) is executed; (2E) parsing the current frame coding-tree-unitby coding-tree-unit, and defining a coding-tree-unit to be parsed in thecurrent frame as a current parsing block; (2F) judging whether thecurrent parsing block is a skip block, wherein if it is, step (2G) isexecuted, otherwise, coding quantization parameter embedded with secretinformation of the current parsing block are parsed and recorded asQP′_(dec) and then a remainder result of QP′_(dec) to 4 is calculatedand recorded as d′_(dec), wherein the d′_(dec) is 0, 1, 2 or 3, and thenthe decimal d′_(dec) is transformed to binary number, values of two bitsextracted from the current parsing block are obtained, such that asecret information extraction process of the current parsing block iscompleted, and then the step (2G) is executed; (2G) regarding a nextcoding-tree-unit to be parsed of the current frame as a current parsingblock, and then returning to the step (2F) till all coding-tree-units ofthe current frame are completely processed, and then step (2H) isexecuted; (2H) regarding a next frame to be parsed of the str.bin_(dec)as a current frame, and then returning to the step (2D) till all framesof the str.bin_(dec) are completely processed, such that secretinformation extraction is completed; and (21) defining extracted valuesof n_(W), bits as encrypted information and recording the encryptedinformation as W′_(dec), here, W′_(dec)=w′_(dec,n) _(W) w′_(dec,n) _(W)₋₁ . . . w′_(dec,i) . . . w′_(dec,2) w′_(dec,1), and then perform an XOR(exclusive OR) operation on a value of each bit of the W′_(dec) and avalue of each corresponding bit of the E, obtaining an XOR result,taking the XOR result as decrypt secret information and recording thedecrypt secret information as W_(dec), here, wherein: theW_(dec)=w_(dec,n) _(W) w_(dec,n) _(W) ₋₁ . . . w_(dec,i) . . .w_(dec,2)w_(dec,1), wherein: the w′_(dec,n) _(W) w′_(dec,n) _(W) ₋₁ . .. w′_(dec,i) . . . w′_(dec,2) w′_(dec,1) respectively represent a valueof the (n_(W))^(th) bit, a value of the (n_(W)−1)^(th) bit, . . . , avalue of the (i)^(th) bit, . . . a value of the second bit and a valueof the first bit of the W′_(dec), each of the w′_(dec,n) _(W) w′_(dec,n)_(W) ₋₁ . . . w′_(dec,i) . . . w′_(dec,2) w′_(dec,1) is 0 or 1,w_(dec,n) _(W) w_(dec,n) _(W) ₋₁ . . . w_(dec,i) . . .w_(dec,2)w_(dec,1) respectively represent a value of the (n_(W))^(th)bit, a value of the (n_(W)−1)^(th) bit, . . . , a value of the (i)^(th)bit, . . . a value of the second bit and a value of the first bit of theW_(dec), each of the w_(dec,n) _(W) w_(dec,n) _(W) ₋₁ . . . w_(dec,i) .. . w_(dec,2)w_(dec,1) is 0 or
 1. 2. The 3D-HEVC inter-frame informationhiding method based on visual perception, as recited in claim 1, whereinin the step (1H-b), through the w′_(i′) and the w′_(i′+1), theQP_(org,j,k) is downwardly modulated to obtain the QP′_(org,j,k) whichcomprises: (b1) finding out all values in an interval of[−3,QP_(org,j,k)] which meet a condition that a remainder result of anabsolute value of each of all the values to 4 is equal to d_(i′); (b2)calculating an absolute value of a difference value of each of all thevalues found out in the step (b1) and the QP_(org,j,k); and (b3) findingout a minimum absolute value of all absolute values calculated in thestep (b2), and assigning a value found out in the step (b1), which iscorresponding to the minimum absolute value, to the QP_(org,j,k); in thestep (1H-b), through the w′_(i′) and the w′_(i′+1), the QP_(org,j,k) isupwardly modulated to obtain the QP_(org,j,k) which comprises: (b1′)finding out all values in an interval of [QP_(org,j,k),54] which meet acondition that a remainder result of an absolute value of each of allthe values to 4 is equal to d_(i′); (b2′) calculating an absolute valueof a difference value of each of all the values found out in the step(b1′) and the QP_(org,j,k); and (b3′) finding out a minimum absolutevalue of all absolute values calculated in the step (b2′), and assigninga value found out in the step (b1′), which is corresponding to theminimum absolute value, to the QP′_(org,j,k).
 3. The 3D-HEVC inter-frameinformation hiding method based on visual perception, as recited inclaim 1, wherein in the step (1H-c), through the w′_(i′), and thew′_(i′+1), the QP_(org,j,k) is downwardly modulated to regain theQP′_(org,j,k), which comprises: (c1) finding out all values in aninterval of [0,QP_(org,j,k)] which meet a condition that a remainderresult of an absolute value of each of all the values to 4 is equal tod_(i′); (c2) calculating an absolute value of a difference value of eachof all the values found out in the step (c1) and the QP_(org,j,k); and(c3) finding out a minimum absolute value of all absolute valuescalculated in the step (c2), and assigning a value found out in the step(c1), which is corresponding to the minimum absolute value, to theQP′_(org,j,k); in the step (1H-c), through the w′_(i′) and thew′_(i′+1), the QP_(org,j,k) is upwardly modulated to regain theQP′_(org,j,k), which comprises: (c1′) finding out all values in aninterval of [QP_(org,j,k),51] which meet a condition that a remainderresult of an absolute value of each of all the values to 4 is equal tod_(i′); (c2′) calculating an absolute value of a difference value ofeach of all the values found out in the step (c1′) and the QP_(org,j,k);and (c3′) finding out a minimum absolute value of all absolute valuescalculated in the step (c2′), and assigning a value found out in thestep (c1′), which is corresponding to the minimum absolute value, to theQP′_(org,j,k).
 4. The 3D-HEVC inter-frame information hiding methodbased on visual perception, as recited in claim 2, wherein in the step(1H-c), through the w′_(i′), and the w′_(i′+1), the QP_(org,j,k) isdownwardly modulated to regain the QP′_(org,j,k), which comprises: (c1)finding out all values in an interval of [0,QP_(org,j,k)] which meet acondition that a remainder result of an absolute value of each of allthe values to 4 is equal to d_(i′); (c2) calculating an absolute valueof a difference value of each of all the values found out in the step(c1) and the QP_(org,j,k); and (c3) finding out a minimum absolute valueof all absolute values calculated in the step (c2), and assigning avalue found out in the step (c1), which is corresponding to the minimumabsolute value, to the QP_(org,j,k); in the step (1H-c), through thew′_(i′) and the w′_(i′+1), the QP_(org,j,k) is upwardly modulated toregain the QP′_(org,j,k) which comprises: (c1′) finding out all valuesin an interval of [QP_(org,j,k),51] which meet a condition that aremainder result of an absolute value of each of all the values to 4 isequal to d_(i′); (c2′) calculating an absolute value of a differencevalue of each of all the values found out in the step (c1′) and theQP_(org,j,k); and (c3′) finding out a minimum absolute value of allabsolute values calculated in the step (c2′), and assigning a valuefound out in the step (c1′), which is corresponding to the minimumabsolute value, to the QP′_(org,j,k).